Record-only merge of r326857 and r326888

These are equal and opposite commits*; one to flip GELI support off by
default and another to flip it back on. They were made to circumvent some
GELI breakage in head that didn't apply to stable/11.

The former commit shows up when looking at MFC candidates for stand/, hence
the desire for this record.

• Equal and opposite except in that r326857 added a comment to zfsldr.S that

likely should not have been added at that time.